They have an awesome chrome extension too, keepa is arguably better than camelcamelcamel, in that it also shows when Amazon went in and out of stock historically, as well as the usual - price history, sales rank, number of sellers, list price & more .

You can set up email alerts for specific-product price drops, use the extension to view product data graphs embedded in amazon product pages, or just use the website to browse for bargains.

I don't even have a cat, but this cat food looked like a bargain for someone!